Apparatus and a method for separating particles from hot gases

ABSTRACT

An apparatus that includes (i) a centrifugal separator assembly and (ii) a fluidized bed reactor having a reactor chamber, the separator assembly being connected to the reactor and provided for separating solid particles from gas discharged from the reactor chamber. The apparatus includes planar peripheral walls defining a vortex chamber, having a rectangular cross section, the vortex chamber having an interior gas volume in which at least two vertical gas vortices can be formed, and the planar peripheral walls including a first wall portion connecting the separator assembly to the reactor chamber, at least two gas outlets, disposed one after the other in the longitudinal direction of the vortex chamber, for discharging cleaned gas from the gas volume, at least one solid particles outlet for discharging separated solid particles from the gas volume, and at least one gas inlet, arranged in the first wall portion, for introducing gas from the reactor chamber into the gas volume. The at least one gas inlet includes at least two inlet ducts which are mainly perpendicular to the first wall portion and arranged side-by-side in the first wall portion within a less than ninety degree sector of one gas vortex within the vortex chamber.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus and a method forseparating particles from hot gases.

The present invention particularly relates to a centrifugal separatorassembly, which may be connected to a reactor, such as a combustor orgasifier, for separating solid particles discharged with flue gases fromits reactor chamber. The peripheral walls of the centrifugal separator'svortex chamber delimit an interior gas volume with at least one gasvortex therein. A first wall portion of the peripheral walls includes aninlet for introducing the flue gases and solid particles entrainedtherein into the vortex chamber. The vortex chamber further includes atleast one gas outlet, for discharging purified gas therefrom, and atleast one particles outlet, for discharging separated solid particlestherefrom.

The present invention more particularly relates to centrifugal separatorassemblies, which are suitable for separating solid particles fromprocess or product gases in fluidized bex reactors, such as circulatingfluidized bed reactors used for combustion or gasification ofcarbonaceous or other fuels.

Conventional centrifugal separators have cyclones delimited bycylindrical peripheral walls and a conical bottom. It has, however,recently been noticed that centrifugal separators can advantageously bemade also of planar wall panels, the vortex chamber formed therebyhaving a non-circular horizontal cross section. U.S. Pat. No. 5,281,398discloses this kind of a centrifugal separator, according to whichparticles entrained in hot gases are separated in a vortex chamberdelimited by a plurality of substantially planar plates or panels, thevortex chamber having a polygonal, preferably quadrate, horizontal crosssection. Such a separator has numerous especially cost saving advantagesover conventional centrifugal separators, it is particularly easy toconstruct, even if made of water tube panels, and it may easily beintegrated with reactor furnaces made of similar wall panels, therebyproviding a compact overall design. Gas is introduced into thenon-circular vortex chamber, through a gas inlet in the side wallthereof, so as to guide the gas as tangentially as possible into the gasvortex formed within the vortex chamber, in order to maximize theswirling or spinning of the gas in the gas vortex.

The advantages of introducing gas tangentially into the vortex chamberis well-known, also in conventional cylindrical cyclones. This advantagehas also been noticed in U.S. Pat. No. 5,070,822 suggesting acentrifugal separator having its vortex chamber centrally located withinthe upper most part of a cylindrical furnace. The centrifugal separatorcomprises a plurality of wing-like elements arranged one after the otheron the upper periphery of the vortex chamber. A plurality of spaced gasinlets is thus formed between the wing-like elements along the entireperiphery of the vortex chamber. The wing-like elements, which may bemade of a ceramic material, are directed so as to guide the plurality ofgas flows through the inlets tangentially into a vortex formed centrallywithin the vortex chamber.

In a centrifugal separator with planar walls, as disclosed in earliermentioned U.S. Pat. No. 5,281,398, the inlet to the separator is avertical slot located so as to lead the gas flow and the solid particlestherein as tangentially as possible towards the vertical gas vortexformed within the vortex chamber. A simple opening in a side wall of thevortex chamber does, however, have a rather poor guiding effect on thegas and solid particles flowing into the vortex chamber. A considerableportion of the gas and solid particles introduced through the openingimmediately deviates from the intended tangential direction and meetsthe gas vortex at an angle substantially greater than zero. This to someextent decreases the swirling velocity of the gas vortex and lowers theseparation efficiency of the system. Some of the solid particles mayalso, if not directed correctly, hit the walls of the vortex chamber atan unfavorable angle, thereby causing heavy erosion.

It has been suggested to insert vertical guide plates around the inletopening in order to increase the horizontal directionality of the gasand solid particle stream, in order to force the gas and solid particlesto flow into the vortex chamber in the intended direction. The guideplates form an inlet duct which has to be rather long, in order for theduct to have a real impact on the direction of movement of the gas andsolid particle stream introduced into the vortex chamber.

The long guide plates or guiding walls are located within the vortexchamber for achieving the desired effect. Such inserts within a vortexchamber have, however, to be very well supported, insulated andprotected in order to endure in the hot surroundings. Large extraconstructions are heavy and have to be well supported and they also haveto be connected firmly so as not to vibrate and decrease strength of theoverall construction. To insert large elements, as suggested, into thevortex chamber goes against the general trend in the manufacturing ofparticle separators, which is to avoid the addition of any extraelements, which take space, have to be supported and protected. There isa need to make an as simple, straightforward and self-supportingconstruction as possible.

Further, it has been noticed in non-circular centrifugal separators,closely integrated with the reactor furnace, i.e., being connected by acommon wall thereto, and having elements therein forming two or more gasvortices within the vortex chamber, that the strength of the common wallbetween the separator and the reactor furnace, especially the strengthto withstand pressure differences between the furnace and the separator,is an important factor. The common wall tends to vibrate unlesssupported. It has, therefore, been suggested to dispose in the vortexchamber a partition or supporting wall, extending from the common wallto the opposite wall between two gas vortices, in order to increase thestrength and suppress vibration. Such a supporting wall, however, alsoconstitutes a rather large extra element within the vortex chamber,which preferably should be avoided.

Non-circular vortex chambers and reactor furnaces may also be builtnon-integrated, i.e., without a common wall, and mechanically connectedto each other only through a distinct inlet duct. This prevents thepressure difference between the reactor chamber and the vortex chamberfrom directly having an impact on a wall in the vortex chamber. An inletduct, if long enough, may further have a positive impact ondirectionality, i.e., it may help to lead the gas and solid particlestangentially into the gas vortex within the vortex chamber. Thenon-integrated construction requires, however, a lot of space and givesrise to a considerable increase in the costs.

There is obviously a need for new solutions, particularly in centrifugalseparators with planar walls, to improve the directionality ororientation of the stream of gas and particles entering a centrifugalseparator, i.e., to introduce the stream of gas and particles into thevortex chamber of the centrifugal separator without the stream beingimmediately spread or scattered, or without causing turbulence in thestream. The desire is to keep together the stream. This should, however,be done with inserts having a limited length, i.e., inserts which do notprotrude so deep into the vortex chamber that they have a negativeimpact on the gas vortex therein. Such new solutions should preferablyalso be cost effective and able to improve the strength of the structurewithout requiring additional space in the vortex chamber.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an improvedcentrifugal separator assembly and method of separating particles fromhot gases.

It is a primary object of the present invention to provide an improvedcentrifugal separator with gas flow guiding means at the inlet forimproving the swirling action of gas, within the vortex chamber.

It is thereby more particularly an object of the present invention toprovide an improved centrifugal separator with guiding means of alimited length for providing an improved directionality of the gas andparticle stream entering the separator.

It is also an object of the present invention to provide a modifiedcentrifugal separator design with improved strength of the centrifugalseparator structure.

It has now been noticed that the horizontal directionality of the streamof gas and solid particles being introduced into a vortex chamber may beincreased not only by providing a long inlet duct, but by providinginstead of one single inlet duct, two or more narrower and shorter inletducts within a certain sector of the vortex. The mere narrowing of oneinlet duct increases—at a certain circulation rate—the forces and energylosses due to the increased pressure difference between the furnace andthe cyclone. But by providing several narrow inlet ducts, the same openarea may be maintained and an increase in pressure difference may beavoided. When utilizing several narrow inlet ducts instead of one singleinlet duct, their length may be made correspondingly shorter, whilestill maintaining the same effect in orientation of the gas stream.Thus, it may be avoided that the inlet ducts have to be made longer thana so-called critical length l_(critical) and penetrate so deep into thevortex chamber that they have an impact on the swirling vortex. Theconstruction may also otherwise be simplified and made less heavy andcostly.

Therefore, in order to fulfill the above and other objects, acentrifugal separator assembly connected to a reactor, such as afluidized bed reactor, comprises according to the preferred embodimentof the present invention besides peripheral walls defining a vortexchamber and at least one gas outlet and at least one solid particlesoutlet,

at least two inlet ducts arranged side by side in a wall, connecting thevortex chamber with the reactor, within a less than 90° sector of eachof the at least one gas vortices formed within the vortex chamber.

The inlet ducts preferably have a length to width ratio l/w>0.8, thelength l being the length of the inlet duct in the gas flow directionand the width w being the mean horizontal cross-sectional width of theinlet duct. The length to width ratio may in some exceptional cases be<0.8, particularly if the critical length of the inlet duct is veryshort. Also, the geometries of the inlet and outlet openings of theinlet ducts have an impact on the length to width ratio. The inlet andoutlet openings may be chamfered if desired.

In a centrifugal separator, the two or more inlet ducts typically haveidentical widths, but may if desired have different widths. The width ofsingle inlet ducts may also vary along their length. The inlet ductsmay, e.g., be funnel-shaped, increasing or decreasing in the flowdirection. The horizontal axes of the two or more separate inlet ductsmay be parallel with each other or form an angle, preferably less than30°, with each other.

The inlet ducts typically are vertical slots having parallel verticalside walls, the height h of a slot being at least twice, typically fivetimes, the mean horizontal cross-sectional width of the slot.

The two or more inlet ducts may easily be formed according to theinvention in an opening, prefabricated in a vortex chamber wall, bydividing the prefabricated opening with one or more vertical partitionwalls. Alternatively, inlet ducts may be prefabricated by casting in aprefabricated wall portion made of a castable material.

The present invention is particularly well suited to be applied invortex chambers having cooled peripheral walls made of water or steamtubes forming a tube system, if desired connected to the mainwater/steam system of the reactor. In cooled walls, the tubes aremechanically connected side by side preferably by fins and in a verticalposition. The one or more partition walls dividing the opening, forproviding two or more inlet ducts according to the invention, maypreferably be made of vertical tubes as well, the vertical tubes formingwithin the opening a partition wall perpendicular to the main plane ofthe peripheral wall. The tubes forming the partition wall are preferablyconnected to the tube system of the peripheral walls.

The one or more partition walls, dividing the opening into two or moreinlet ducts, form a delimiting wall in each of two adjacent inlet ducts.The outermost delimiting wall of the inlet ducts, i.e., of the inletducts located adjacent to the vertical sides of the opening, may on theother hand be formed of tubes bent out of the main plane of theperipheral wall, when forming the opening.

The length of the inlet ducts, formed of partition walls or other inletduct delimiting walls, should typically be greater than the thickness ofthe peripheral wall of the vortex chamber. Thereby, the one or morepartition walls and/or the other delimiting walls used to form the inletducts protrude from the plane of the peripheral wall, preferably intothe vortex chamber, but could protrude in the other direction ifdesired. The delimiting walls are typically formed of tube panels madeof greater than three, preferably, greater than five tubes, mechanicallyconnected side by side by fins.

The vortex chamber is according to a preferred embodiment of the presentinvention made of mainly planar peripheral walls and has a rectangularor square horizontal cross section, the peripheral walls of the vortexchamber comprising

a common wall portion between the vortex chamber and the reactorchamber, said common wall portion including the first wall portion,

first and second side walls, perpendicular to the common wall portionand

a third side wall opposite to the common wall portion and parallel tothe common wall portion, and

the peripheral walls being formed of vertical tubes connected side byside, preferably by fins, and forming a peripheral wall tube system.

In an embodiment in which the vortex chamber has a square cross section,the gas outlet is disposed mainly in the middle of the top portion ofthe vortex chamber, and the inlet ducts are formed in an opening in thecommon wall portion adjacent to the first side wall. If desired, theinlet ducts may be located at the end of the common wall adjacent to thefirst side wall and perpendicular to the common wall. Then, a portion ofthe first side wall of the vortex chamber may form a side wall in one ofthe inlet ducts.

The vortex chamber has according to a most preferred embodiment of thepresent invention a rectangular cross section. Two gas outlets are thendisposed one after the other in the longitudinal direction in the topportion of the vortex chamber, for providing two gas vortices within thegas volume in the vortex chamber. Inlet ducts are formed in an openingin the common wall portion between the two adjacent vortices. The inletducts are preferably formed in the common wall equidistant from the twovortices, for introducing gas into both of the two adjacent vortices.The delimiting walls of the inlet ducts are formed of

one partition wall, disposed perpendicular to the main plane of thecommon wall portion, and of

vertical tubes bent out of the plane of the common wall portion formingthe outermost side walls in the inlet ducts.

The partition wall is formed of greater than three, preferably greaterthan five, vertical tubes mechanically connected side by side in a row.The tube construction of the partition wall is preferably covered by alayer of protecting refractory material, the thickness of the layerbeing chosen according to need. The refractory material may be shaped,e.g., streamlined, to provide advantageous flow properties in the inletducts and at their inlets and outlets.

The partition wall structure is especially useful in rectangular vortexchambers when it is constructed so that it also increases the strengthof the common wall between a furnace and a centrifugal separator. Thepartition wall, dividing the opening, is typically mechanicallyconnected to the common wall portion above and below the opening. Aprolongation of the partition wall may additionally be mechanicallyconnected to the lower part of a third side wall, opposite to the commonside wall, of the vortex chamber, in order to increase the support ofthe common wall. The prolongation may on the other had alternatively oradditionally be connected to supporting structures of the reactorchamber or the vortex chamber.

If desired, the first wall portion connecting the vortex chamber withthe reactor chamber, may be made of a mainly homogeneous castablematerial. Then, the inlet ducts may be formed by casting.

These inlet ducts, which are formed by casting, may also have a lengthto width ratio l/w>0.8, as inlet ducts made in tube walls. The inletducts usually are parallel with each other and perpendicular to the mainplane of the wall. The inlet ducts may, however, in some cases be madeso as to form an angle less than 90° with the main plane of the wall.Then, also two single inlet ducts may be disposed to form an angle witheach other, e.g., an angle of about 5° to 60°.

The present invention, as described above, provides an improvedcentrifugal separator with gas flow guiding means at the inlet thereoffor improving the swirling action of gas within the vortex chamber. Theimproved swirling action is achieved with relatively short inlet ducts,which act as non-spreading nozzles. The nozzles form controlledpre-oriented gas jets, which introduce the gas in a desired directionand into a desired location within a limited space of the vortexchamber. The present invention thereby particularly provides acentrifugal separator in which the optimization of the directionality ofgas and particles entering the separator is accomplished with aconstruction in which disturbance on the swirling action of the vortexis minimized.

Additionally, the present invention provides means for improving thestrength of the centrifugal separator structure. The present inventionparticularly provides means for increasing the strength of the commonside wall between the vortex chamber and the reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above description, as well as further objects, features andadvantages of the present invention will become more apparent from thefollowing detailed description of the presently preferred, butnonetheless illustrative embodiments in accordance with the presentinvention when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a schematic side view, partly sectional and partly elevated,of a circulating fluidized bed reactor with a centrifugal separatoraccording to the present invention;

FIG. 2 is a cross-sectional view of the upper part of the centrifugalseparator of FIG. 1 taken along line A—A thereof;

FIG. 3 is a cross-sectional view of the separator of FIG. 2 taken alonglines B—B thereof; and

FIGS. 4-6 are views like that of FIG. 3 for alternative embodiments ofcentrifugal separators according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a circulating fluidized bed reactor comprising areactor chamber 10, a centrifugal particle separator (cyclone) 12 and areturn duct 14 for returning separated particles back to the chamber 10.The cross section of the reactor chamber 10 is rectangular, as can betaken from FIG. 3. The reactor chamber 10 is made of water tube walls,only long walls 16 and 18 of which are shown in FIG. 1. The water tubewalls are formed of vertical water tubes connected by fins in a mannerknown per se, e.g., as so-called membrane wall panels.

The upper part of wall 18 is bent to form a ceiling 20 of the reactorchamber 10. The walls in the lowermost section of the reactor chamber 10are protected with refractory 22. One inlet 23 only, for solid materialsuch as fuel, is shown, although there may be several different inlets.The bottom of reactor chamber 10 is formed of a distribution plate 24,which is equipped with nozzles or openings 26 for introducing fluidizinggas from an air plenum chamber 28 into reactor chamber 10 formaintaining a fluidized bed of solid particles therein. Fluidizing gas,e.g., air, is introduced into the reactor chamber 10 at such a high ratethat it causes a substantial portion of the bed material to continuouslyflow together with the gas through the upper section of chamber 10 andthrough an inlet opening (e.g., slot) 30 disposed in the upper sectionof chamber 10 into particle separator 12.

The particle separator 12 is a multivortex centrifugal separator with avortex chamber 12 with a gas volume having two parallel, vertical gasvortices formed therein, for separating particles from gas introducedfrom the reactor chamber 10 into the vortex chamber. The vortex chamber12 defining the separator comprises planar, as can be seen in FIG. 3,primarily rectangular water tube side walls 32, 34, 36 and 38. Theseside walls 32, 34, 36, 38 are also made of joined, vertical water tubes37 mechanically connected to each other by fins 39 (as shown in anelevated detail in FIG. 2). The vortex chamber 12 has according to FIG.1 one long wall 32 in common with reactor chamber 10, i.e., a part ofthe wall 16 of reactor chamber 10 constitutes wall 32 of the vortexchamber. In some cases, distinct walls for both reactor chamber 10 andvortex chamber 12 may be used.

The upper parts of the side walls 32, 34, 36, 38 in the vortex chamberdefining the gas volume are preferably vertical and planar and form anupper section 43. The lower part of the long wall 36, opposite to thecommon side wall 32, is bent towards the common wall for forming afunnel-shaped lower section 45 of the vortex chamber. By this structure,an asymmetric, long, slightly funnel-shaped gas volume 44 (see FIG. 1)is formed, the bottom part thereof forming a solids outlet 46.

Solids outlet 46 serves as an inlet into return duct 14. The long sidewalls of the return duct are formed by downward extensions of walls 32and 36 of the particle separator 12. The end walls of the return duct 14are correspondingly formed by downward extensions of the side walls 34and 38. Only a portion of the ends walls 34 and 38, having a width ofreturn duct 14, continues downwardly, thereby forming a return duct. Thelower part of return duct 14 is in communication with the lower sectionof the reaction chamber 10 via an L-bend 48 for returning solidsseparated in separator 12 into the bottom of the reactor chamber 10;other types of solid flow seals may alternatively be used.

In the upper section 43 of the vortex chamber, two successive gas outletducts 54 and 56, for the discharge of purified gas from the gas space ofthe vortex chamber 12 are disposed in openings 50 and 52, as shown inFIGS. 2 and 3. The gas outlet ducts 54, 56 in separator 12 may be madeof heat resistant steel, be cooled or be made of ceramic material, inorder to resist hot conditions in separator 12. The purified gases maybe discharged in a manner known per se from the separator 12 throughduct 60, passing heat recovery surfaces 62, and a convection section.

The side walls 32, 34, 36, 38 of the vortex chamber may be protected bya thin layer of heat and abrasion resistant refractory material, notshown in the drawings.

The inlet opening 30, formed in a first wall portion 32′ in the commonwall 32, is divided by a partition wall 70 to form two inlet ducts 30′,30″, and is located within a 90° sector β of both gas vortices formedbelow gas outlets 54 and 56. The opening 30 is formed at the samedistance from both vortices, between the vortices, approximately in themiddle of the common wall 32 between chamber 10 and chamber 12.

At the vertical sides of the inlet opening 30, water tubes 37′ of thewater tube wall 32 are bent into the vortex chamber, as best seen inFIG. 3, so that the inlet delimiting vertical side walls 40, protrudinginto the vortex chamber, are formed. The side walls 40 are typicallyperpendicular to the main plane of wall 32, but could be inclined toform an angle greater than 60° with the main plane of wall 32. The sidewalls may be inclined so as to decrease the width of the inlet duct orso as to widen the inlet duct. A vertical partition wall 70, made oftubes 37″, is disposed at the center of the slot-like opening 30, thepartition wall dividing the opening in two similar inlet ducts 30′ and30″. The partition wall is slightly longer than the side walls in thehorizontal direction. The partition wall 70 and the walls 40 form thevertical delimiting walls for the two inlet ducts 30′ and 30″ formed inthe opening.

The tubes 37″ of the partition wall 70 are mechanically connected towall 32 above and below the inlet ducts 30′ and 30″ and extend up to aheader 74 at ceiling 62 of separator 12 and down to a header 72 belowthe lower part 45 of separator 12, as shown in FIGS. 1 and 2. The upperpart of tubes 37″ may if desired reach through duct 60 and be connectedto a header arranged above or on the external side of the duct. At theirlower part, the tubes 37″ of partition wall 70 are bent out from thewall 32 and through the outer wall 17 of return duct 14, as shown inFIG. 1, and connected to a separate external header 72. If desired, thelower part of the tubes 37″ may be bent out from the wall 32 already ata higher level than shown in FIG. 1, and may be made to protrude throughthe lower part of separator wall 36, thereby providing a stiffeningmechanical connection between opposite walls 32, 36 in the separator. Itmay, on the other hand, not be necessary to bend the lower part of thetubes 37″ at all if the tubes are connected at their lower part to aheader located within or in connection with the return duct 14. Headers74 and 72 may be supported (not shown in the drawings) so that the tubes37″ increase the strength of wall 32 and increase its ability to bearthe pressure difference between furnace 10 and separator 12.

The inlet ducts delimiting walls 40 and the partition wall 70 define awidth “w” of each of the two inlet ducts 30′ and 30″ formed in theopening 30. Delimiting sidewalls 40 and partition wall 70 extendinwardly from the common wall 32 between the reactor chamber 10 and thevortex chamber 12 into the vortex chamber a distance “l” which definesthe length of the inlet ducts in the flow direction, e.g., a path lengthof the stream of gas and particles within slot 30′ or 30″. The ratio ofinlet duct length to width l/w gives an indication of the horizontaldirectionality of the gas and solid particle stream flowing through theinlet duct. The larger the ratio the better the directionality. Theratio l/w is preferably greater than 0.8. At an inlet having two inletducts, the ratio may be about one, but may be even greater than one.

The partition walls are in most cases preferably made as thin aspossible in order to keep the total width w_(tot), i.e., the width ofthe first wall portion with the inlet ducts, as small as possible, inorder to allow for the use of as long of inlet ducts as possible withoutthe incoming gas stream interfering with the swirling motion of the gasvortex within the vortex chamber. The critical length of the inletducts, i.e., maximum length, of inlet ducts not interfering with thevortex, decreases as the shortest distance between the inlet end of theinlet duct and the vortex decreases. Therefore, inlet ducts should belocated in the common wall portion as far away from the vortex aspossible. This can be done by squeezing the inlet ducts into an as smalla space as possible, i.e., by utilizing as thin of partition walls aspossible.

In the embodiment shown in FIGS. 1-3, the directionality can be stillimproved by increasing the length l of walls 40 and 70, or by increasingthe thickness of the refractory layer on wall 40 and/or wall 70 andthus, decreasing the width w of the inlet ducts. The total open areamust, however, be maintained.

If desired, e.g., in order to provide more open area without having toincrease the length of the inlet ducts, more than two inlet ducts may beformed. Then, two or more partition walls are used to divide theopening. Typically, the partition walls 70 and the delimiting side walls40 are of different horizontal lengths, the partition wall being longerin the horizontal direction than the side walls. The walls could, ofcourse, if desired, be of the same length, and the partition wall couldeven be shorter than the side walls. The partition wall 70 is usuallymade longer than the side walls in order to still increase itsstrengthening effect on the common wall 32.

At the external sides of the delimiting side walls 40, guiding means areprovided, as generally shown by a reference number 33. The guiding meansguide a gas vortex between the common wall 32 and sidewalls 40 so thatthe flow direction of particles separated from gas in the gas vortex issmoothly changed from generally along the interior of the first wall 32to substantially perpendicular to the first wall 32 at the gas inlet 30(i.e., substantially tangential to the gas vortex in the gas volume andalong the stream introduced at slot 30).

Instead of using the concept depicted in FIGS. 1-3, it may sometimes bepreferable to use a double-vortex separator with two inlet openings, asshown in FIG. 4 or a one single vortex separator as shown in FIGS. 5 and6.

In the embodiment depicted in FIG. 4, there are two inlet openings 30 inthe separator. The openings are made in the ends of common wall 32 nextto side walls 34 and 38, the side walls forming delimiting walls for theoutermost inlet ducts 30″. The partition walls 70 and 70′ are disposedvery close to walls 34 and 38 and do not essentially increase thestrength of wall 32. Thus, the supporting of the upper and lower ends ofthe partition walls 70 and 70′ is not as critical a factor as may be inthe embodiment illustrated in FIGS. 1-3. Each of the two openings 30,each including two inlet ducts, is located in a 90° sector of one of thevortices, i.e., in a 90° sector of that particular vortex being closerto the inlet.

FIG. 5 shows a further alternative embodiment of the present invention.Three inlet ducts are formed in an inlet opening in a separator having asquare horizontal cross section. A single vortex is formed in the vortexchamber. This embodiment illustrates the use of more than one partitionwall 70 to provide more than two inlet ducts. Otherwise, this embodimentcorresponds to that in FIG. 4.

FIG. 6 illustrates yet another embodiment of the present invention,wherein a single vortex is formed and the inlet ducts are constructedfrom slip casting mass. The advantage of using the casting technique isthat it makes it possible to easily and with great accuracy form up tothree to eight inlet ducts, even ducts of different forms and beingdisposed at different angles. The inlet ducts are all formed within a90° sector of the vortex formed in the vortex chamber.

In the embodiment shown in FIG. 6, the first inlet duct 80 closest tothe first side wall 34 is parallel with that side wall 34 andperpendicular to the side wall 32 connected to the reactor chamber. Thenext inlet duct 80′ is not parallel with wall 34 but slightly inclinedso as to guide the gas and solid particle flow therethrough toward thewall 34. Next inlet duct 80″, further away from the side wall 34 is evenmore inclined and the last inlet duct 80′″, most distant from side wall34 is most inclined. The different inlet ducts introduce gas and solidparticle jets tangentially toward the vortex formed in the vortexchamber, the jets, however, touching the vortex tangentially atdifferent locations of the less than 90° sector. Thus, the differentjets enhance the swirling motion of the vortex. The jets are formed soas to interact with vortex 66 as smoothly as possible.

The present invention provides an effective centrifugal separator andmethod of centrifugally separating particles particularly in polygonalmultivortex separators, but can also be used to enhance swirling motionin cylindrical centrifugal separators. The present invention minimizesmany of the drawbacks of prior art separators. The present inventionparticularly sets out to decrease the negative impact introduction ofthe gas and solid particle stream may have on the separation efficiencyof the vortex. The swirling motion of the vortex may be improved withless space consuming inlet ducts than what has been suggested earlier.The present invention simultaneously provides an improvement to theconstruction of the centrifugal separator, the guiding elements nothaving to protrude very deep into the vortex chamber and the guidingelements (inlet duct considerations) adding to the strength and rigidityof the vortex chamber.

While the invention has been shown herein and described in what ispresently believed to be the most practical, preferred embodimentthereof, it will be apparent to those of ordinary skill in the art thatmany modifications may be made thereof within the scope of theinvention, which scope is to be interpreted broadly so as to encompassall equivalent structure and methods.

What is claimed is:
 1. An apparatus comprising (i) a centrifugalseparator assembly and (ii) a fluidized bed reactor having a reactorchamber, the separator assembly being connected to the reactor andprovided for separating solid particles from gas discharged from thereactor chamber, said apparatus comprising: planar peripheral wallsdefining a vortex chamber, having a rectangular cross section, saidvortex chamber having an interior gas volume in which at least twovertical gas vortices can be formed, and said planar peripheral wallsincluding a first wall portion connecting the separator assembly to thereactor chamber; at least two gas outlets, disposed one after the otherin the longitudinal direction of the vortex chamber, for dischargingcleaned gas from the gas volume; at least one solid particles outlet fordischarging separated solid particles from the gas volume; and at leastone gas inlet, arranged in the first wall portion, for introducing gasfrom the reactor chamber into the gas volume, said at least one gasinlet including at least two inlet ducts which are mainly perpendicularto the first wall portion and arranged side by side in the first wallportion within a less than ninety degree sector of one gas vortex withinthe vortex chamber.
 2. An apparatus according to claim 1, wherein theinlet ducts have a length to width ratio l/w>0.8, the length l being thelength of the inlet duct in the gas flow direction and the width w beingthe mean horizontal cross-sectional width of the inlet duct.
 3. Anapparatus according to claim 1, wherein the inlet ducts are verticalslots having parallel vertical inlet duct delimiting walls, the verticalheight h of a slot being at least twice the mean horizontalcross-sectional width of the slot.
 4. An apparatus according to claim 3,wherein the vertical height h of a slot is ten times the mean horizontalcross-sectional width of the slot.
 5. An apparatus according to claim 1,wherein the at least two inlet ducts are formed in an opening in thefirst wall portion by dividing the opening with at least one verticalpartition wall.
 6. An apparatus according to claim 5, wherein theperipheral walls of the vortex chamber are tube walls, made of aplurality of vertical tubes connected to form a tube system, and the atleast one partition wall dividing the opening is made of greater thanthree vertical tubes connected to said tube system.
 7. An apparatusaccording to claim 6, wherein the at least one partition wall dividingthe opening is made of greater than five vertical tubes connected tosaid tube system.
 8. An apparatus according to claim 6, wherein the atleast one partition wall is disposed within the opening mainlyperpendicular to the main plane of the first wall portion.
 9. Anapparatus according to claim 6, wherein a vertical inlet duct delimitingside wall in the at least one of the inlet ducts is formed of verticaltubes bent out of the plane of the first wall portion, the tubes beingbent into or out of the vortex chamber to form an inlet duct delimitingside wall perpendicular to the main plane of the first wall portion. 10.An apparatus according to claim 9, wherein the vertical inlet ductdelimiting side wall is made of greater than three tubes, which areconnected to the tube system of the peripheral walls.
 11. An apparatusaccording to claim 10, wherein the vertical inlet duct delimiting sidewall is made of greater than five tubes, which are connected to the tubesystem of the peripheral walls.
 12. An apparatus according to claim 1,wherein the vortex chamber comprises: a common wall portion between thevortex chamber and the reactor chamber, said common wall portionincluding the first wall portion; a first side wall and a second sidewall, perpendicular to the common wall portion; and a third side wallopposite to and at least in its upper part parallel to the common wallportion, wherein the peripheral walls are formed of vertical tubesmechanically connected side by side and forming a peripheral wall tubesystem.
 13. An apparatus according to claim 12, wherein the peripheralwalls are mechanically connected side by side by fins.
 14. An apparatusaccording to claim 12, wherein the inlet ducts are formed in an openingin the common wall portion between two adjacent vortices, forintroducing gas into both of the two adjacent vortices.
 15. An apparatusaccording to claim 14, wherein the vertical delimiting walls of theinlet ducts are formed of at least one partition wall, disposedperpendicular to the main plane of the common wall portion and formed ofvertical tubes connected to the peripheral wall tube system, andvertical tubes bent out of the plane of the common wall portion, thetubes being bent into or out of the vortex chamber to form an inlet ductdelimiting side wall, inclined greater than sixty degrees to the mainplane of the common wall portion.
 16. An apparatus according to claim15, wherein the inlet duct delimiting side wall is perpendicular to themain plane of the common wall portion.
 17. An apparatus according toclaim 14, further comprising two gas outlets disposed within the vortexchamber, for forming two gas vortices therein, one vertical openingformed in the middle of the common wall portion, and two inlet ductsformed in the opening by (i) disposing a vertical partition wall in themiddle of the opening, for forming a first inlet duct delimiting wall ineach of the two inlet ducts, and (ii) bending vertical tubes at theopening area out of the plane of the common wall portion, for forming asecond inlet duct delimiting wall in each of the two inlet ducts.
 18. Anapparatus according to claim 14, wherein greater than three verticaltubes are bent out of the plane of the common wall portion.
 19. Anapparatus according to claim 18, wherein the vertical tubes bent out ofthe plane of the common wall portion are used for forming the verticaldelimiting side walls of the inlet ducts.
 20. An apparatus according toclaim 14, wherein greater than five vertical tubes are bent out of theplane of the common wall portion.
 21. An apparatus according to claim20, wherein the vertical tubes bent out of the plane of the common wallportion are used for forming the vertical delimiting side walls of theinlet ducts.
 22. An apparatus according to claim 14, wherein thepartition wall is mechanically connected to the common wall portionabove and/or below the inlet ducts and additionally by its prolongationto the lower part of the third side wall of the vortex chamber.
 23. Anapparatus according to claim 14, wherein the partition wall ismechanically connected to the common wall portion above and/or below theinlet ducts and additionally by its prolongation to supportingstructures of one of the reactor chamber and the vortex chamber.
 24. Anapparatus according to claim 1, wherein the first wall portion is madeof a mainly homogeneous castable material and the inlet ducts are formedby casting in the castable material.
 25. An apparatus according to claim24, wherein the inlet ducts have a length to width ratio l/w>0.8, thelength l being the length of the inlet duct in the gas flow directionand the width w being the mean horizontal cross-sectional width of theinlet duct.
 26. An apparatus according to claim 24, wherein the axes ofthe inlet ducts are parallel.
 27. An apparatus according to claim 24,wherein the axes of at least two inlet ducts form an angle between 5° to60°.
 28. A method for separating solid particles from gas dischargedfrom a reactor chamber, utilizing a centrifugal separator that includesa vortex chamber having a rectangular cross section and being delimitedby peripheral walls including a planar first wall portion and having atleast two gas outlets, at least one solid particles outlet and a gasinlet means arranged in the first wall portion, the method comprising:discharging a gas and solid particle stream from the reactor chamber andintroducing the stream through the gas inlet means into the vortexchamber; separating solid particles from the gas in at least two gasvortices formed in the vortex chamber; discharging separated solidparticles from the vortex chamber through the at least one solidparticles outlet; discharging purified gas through the at least two gasoutlets; and dividing the gas and solid particle stream discharged fromthe reactor chamber in the gas inlet means into at least two adjacentstreams and introducing the at least two streams mainly perpendicular tothe first wall portion and within a less than ninety degree sector of agas vortex into the vortex chamber.
 29. A method according to claim 28,further comprising guiding the at lest two gas and solid particlestreams through inlet ducts having a length to width ratio l/w>0.8.